Viscometer



Dec 20, 1949 w. G. BECHTEL Erm., 2,491,539

VISCOMETER Filed Jan. Q, 194s` 0 WZef" C. ecz, Carl C. Kesler) PatentedDec. 20, 1949 UNITED STATES PATENT OFFICE VISCMETER poration oi. IndianaApplication January 9, 1948, Serial No. 1,358

(Cl. i3-59) 5 Claims.

This invention relates, generally, to viscometers, and it has particularrelation to continuous reading viscometers, particularly useful formeasuring the viscosities of cooked aqueous dispersions of starch or itsmodications.

Although the invention is particularly useful in connection withdetermining viscosities of aqueous starch dispersions, and will bedescribed with specic relation thereto, it will be understood that theinvention may also be used in connection with the determination andmeasurement of viscosities of other liquid masses.

Cooked aqueous dispersions of starch consist of swollengranules,fragments formed by disintegration of granules, and dissolved matterwhich has been leached from the swollen granules. Such dispersions ofstarch are known as starch pastes. Since starch pastes are not truesolutions they do not have Newtonian flow properties. That is, they donot follow the laws of viscous flow which have been developed for pureliquids and true solutions. In particular the viscosities of starchpastes are not constant for all rates of shear, but are shear-dependentviscosities. Such shear-dependent viscosities are frequentlydistinguished from the property of true viscosity by referring to themas apparent viscosities or consistencies.

The apparent viscosity of starch pastes has long been used as a means offactory control of the process of modifying starches chemically, and forthe specification and standardization of starch products of differentcommercial grades. Consumers of starch and its chemical and physicalmodifications have likewise used tests of apparent viscosity todetermine the suitability of the properties of starches for certainspecic uses.

Determinations of the apparent viscosity of starch pastes have been madein viscometers of many kinds. For pastes in the concentration rangeapproximating that of common industrial uses, apparent viscosity hasbeen determined most frequently `in orice viscometers such as the Scott,or by means of pipettes such as the Dudley. In other instances fallingball, rotational, or capillary viscometers have been used.

The apparent viscosity of dispersons such as starch pastes depends onthe history of the sample prior to the test. The rate of cooking thesample, the temperature to which it is cooked, the rate and type ofstirring, the length of the cooking period, and the total elapsed timefrom the start of cooking until the viscosity test is made all have aneil'ect on the results of the test. These in order for replicate teststo produce results which are in close agreement. In addition,precaustions must be taken to` prevent loss of water due to evaporationduring cooking, for this 'will alter the concentration of the paste.

It has been difficult to make precise and reliable measurements of theapparent viscosity of vstarch pastes when rate of heating, iinal pastetemperature, and time of cooking are controlled by the operator andstirring is done manually. For with such methods there are variations ofexperimental conditions from one test to another. This has frequentlyled to a lack of close agreement in replicate tests.

Furthermore, the apparent viscosity of materials such as starch pastesdepends on the rate of shear employed in the viscometer. The greater therate of shear the lower is the value obtained for the apparentviscosity. For this reason results of viscosity tests will give accuratevalues for direct comparison of products only when all tests areconducted at the same rate of shear. In any eiliux viscometer, such asan orifice vis-- cometer, rate of shear varies with the rate of flow ofthe uid and thus varies with the viscosity of the starch paste. Pastesof higher viscosity are tested in such viscometers at lower rates ofshear than are those of lower viscosity.

An additional limitation of such methods for testing starch pastes isthat only a single test of apparent viscosity after an arbitrary periodof cooking can conveniently be made. Since the viscosity of a starchpaste generally changes continuously with cooking and agitation, such asingle test is inadequate to characterize the flow properties of thematerial.

More recently there has been developed a type of viscometer in whichviscosity is determined continuously during the cooking of the paste andthe result is either indicated on a scale or recorded automatically on achart. Among the diilloulties which have heretofore limited theapplication of such viscometers are: (l) lack of sensitivity in therange of low viscosities, or lack of suilicient range to enable tests tobe made over the range of viscosities required for industria-l testing;(2) excessive evaporation of water from the paste during the cookingperiod, especially if tests are conducted for a long period of time: (3)non-uniform temperature vthroughout the entire quantity of paste due tothe methods employed in heating and stirring the paste; and (4)non-uniform dispersion of the starch solids with tendency for them tothicken and adhere to the factors must be controlled with greatprecision 56 container surfaces.

A primary object of the invention is the provision of a unit for use inviscosity measuring apparatus which unit insures that a sample of fluid,the viscosity of which is being determined, will be uniformly agitatedso that substantially uniform temperature will be maintained throughoutthe sample and the consistency of the sample throughout all portionsthereof will be substantially uniform.

An important object of the invention ls the provision of a unit for usein viscosity measuring apparatus whereby the viscosity of a fluid samplemay be continuously determined over a relatively long period of time,during which a constant rate of shear is maintained.

It is a further object of the invention to provide a means for thecontinuous determination of the apparent viscosities of materials suchas starch pastes during cooking and cooling of the same, at a constantrate of shear, and with a high degree of sensitivity and precision.

It is a further object of the invention to cook a material such asstarch paste under automatically controlled conditions of agitation,rate of heating, and final temperature, and to so minimize theevaporation of water during cooking that the concentration of the pastewill remain essentially unchanged over a long period.

It is a further object of this invention to prolvide means for thetesting of starches in the lower range of concentrations of theirindustrial applications, as well as at higher concentrations, and to dothis with adequate precision and ac curacy for industrial testing.

Still another object of the invention is the previslon of means forcontinuously determining the viscosities of materials such as starchpaste in such a manner as to maintain an essentially uniform temperaturethroughout the sample and prevent the building up of adherent layers ofpasted starch on the interior of the sample container, thereby promotingeiiicient and rapid transfer from the surrounding paste medium whilemaintaining the consistency of the sample substantially uniformthroughout all parts thereof.

Other objects of the invention will, in part, be obvious and willin partappear hereinafter.

For amore complete understanding of the nature and scope of theinvention, reference may now be had to the following detaileddescription thereof taken in connection with the accompanying drawingwherein the single figure is, in part, a vertical sectional view througha, unit for use in viscosity measuring apparatus and forming thepresently preferred embodiment of thc invention, with certain associatedpieces of apparatus being shown diagrammatically.

Referring now to the drawing, the reference numeral I designates,generally, a unit for use in viscosity measuring apparatus andconstructed in accordance with the principles of the present invention.The unit I0 is shown in association with a torque meter or dynamometerII and a sample cup or container I2 supported in a water bath I3.

The water bath I3 is in the form of a tank I4 formed preferably of poorheat conducting material such as glassA or stoneware, o'rsuitablyinsulated metal. The tank I4 is supported on a table top or othersupport I5.

Water is generally used as the heating medium n 1n the tank u, but othersuitamenqulds may be used. Water may be heated by an electrical ,heatingelement I1 having two terminals IB'and 4 2l extending through the bottomof the tank Il in sealed insulated relationship therewith. The heatingelement may be thermostatically controlled whereby the temperature ofthe water may be regulated and controlled as desired.

The tank I4 is provided with an overflow connection 2l and a drain cock22. A Weir 23 is provided around the inner opening of the connection 2lfor the purpose of maintaining a definite level of water within the tankIl. If it is desired to cool the water of the water bath I3, this may beaccomplished by turning of! the heater I1 and introducing cool waterthrough the drain cock 22 while allowing it to flow over the Weir 23 andout through the overflow connection 2|.

The tank I4 is provided with a-cover 24 having a central opening thereinof relatively large diameter and defined by a collar 25 secured to thecover. The sample cup I2 has an outwardly flared llip 26 which rests onthe top of the collar 23 so as to sup'po'rt the cup I2 within the waterbath llas shown.

The container cup i2 may be in the form of a glass beaker or a metalcup. The beaker or container I2 is provided with a cover 21 having acentral opening 28 therein to accommodate the unit I0 and having anannular shaped condenser ring 30 secured to the under side thereof. Thecover 21 thus serves as an air condenser for water vapor evaporated fromthe contents of the container I2. The vapor condenses on the condenserring 30 and drips back into the sample, thereby maintaining the watercontent thereof. It will be apparent that the cover 21 can be providedin a number of designs having effective condensing surfaces. Forexample, the cover 21 may be provided with connections 29-29 which mayserve as inlet and outlet connections through which al coolant such aswater or air may be circulated.

The unit I0 includes a scraper indicated generally at 3l disposed withinthe container I2 and carried on the lower end of a hollow shaft 32. Apropeller or agitator 33 is located within the scraper 3l and is mountedon the lower end of a shaft 34 which fits within the hollow shaft 32.

The scraper 3l has a rectangular frame 3l having elongated end members36-36. Scraper blades 31-31 are carried on the sides 36 so as t0 bemovable relative thereto. The scraper blades 31 are secured to the frameends 36 by means of ears 38 through which pins 39-39 from the oppositeends of the sides 36- project, as shown. The scraper blades 31 serve toscrape the side wall of the container i2 so as to remove films ordeposits of the sample which may tend to build up thereon.

A bottom scraper blade 4U is supported between the bottom ends of thesides 36 by means of the pins QI-II. This bottom blade 4I! serves toscrape the bottom of the container I2 and move the material toward thecenter thereof.

Both the scraper 3I and the propeller 33 serve to agitate the contentsof the container I2 so as to maintain the contents uniformly mixedthroughout.

A thermometer l2 carried by a stopper 43 fltting in an opening providedtherefor in the cover 21 is used to measure the temperature of thecontents of the container I2.

The shafts 32 and 34 are provided in upper and lower sections which arecoupled together 7&54 at the coupling 43.. This arrangcmentpermits theshafts to be disconnected at the coupling 43 so that the upper portionof the viscometer apparatus may be swung over the water bath I3. therebypermitting the container cup I2 to be removed from or placed in thewater bath I3.

In order that the upper portion of the inner shaft 34 may be heldstationary while the lower portion is connected or disconnectedtherefrom, a pair of pins 44-44 are provided which are normally springretracted from the shaft 34 but which may be pressed together so as tohold it stationary. I

The inner shaft 34 is supported within the hollow shaft 32 by upper andlower ball bearing units 43 and 4E, respectively. The hollow shaft 34 issupported in the depending sleeve portion 41 of a housing 48 by upperand lower ball bearing units 50 and 5I, respectively. The housing 43 maybe supported on a post or other conventional support means, not shown.

'I'he hollow shaft 32 is provided adjacent its upper end with a wormgear 52 rigidly secured thereto and disposed in driving relationshipwith a worm 53 journaled within the housing 48 on a support indicated bythe reference numeral 34. The worm 53 is adapted to be driven at aconstant speed by a synchronous motor indicated diagrammatically at 55and interconnected in driving relationship with the worm 53 by a beltI3. It will be understood that instead of being connected with thesynchronous motor 55, worm 53 may be connected with any other source ofpower and by any other means of transmission which will drive the wormat a uniform speed.

A bracket 51 is secured to the upper end of the hollow shaft 32 by meansof a collar 58. The bracket 5l is provided with a set of ball bearings3l, 5I which support a vertical shaft 62 carrying a planet wheel or gear63 on the upper end thereof.

The planet wheel 53 intermeshes with a sun wheel or gear G4 carried onthe lower end of a vertical shaft 65 supported in a bearing 65 carriedin the housing 48. A drum 61 is secured to the upper end of the shaft 65and this drum is connected by a cable IE8 with a torque meter ordynamometer II.

The torque meter II may be either an indicating type of meter of knowntype or a recording type of meter of known type. Preferably, the torquemeter II is of the type having a quadrant balance, provided with aseries of easily interchangeable auxiliary weights. The auxiliaryweights may be interchanged without necessitating recalibration of thedynamometer thereby greatly extending the range of the torque meter I I.Weights may be interchanged before starting a test or during a testwithout interrupting it.

Torque meters of the type including a quadrant balance, both of therecording and indicating type, are known and available.

The torque meter I I serves to prevent the drum 31 and the sun wheel $4from rotating, and in so doing measures the torque required to hold thesun wheel 34 from turning.

A gear wheel 'III is carried on the shaft 62 underneath the planet wheel63. 'I'he gear 10 intermeshes with a gear 1l carried on the upper endoi' the inner shaft 34.

It will be apparent that the gear wheels 63, 54, 13 and 1I togetherconstitute a sun and planet differential unit.

In operation, the viscosity measuring apparatus shown in the drawingoperates in the following manner:

The water bath I3 is filled with water and preheated to the desiredtesting temperature by means of the thermostatically controlled heatingelement I'I. A sample of material such as starch paste is then put inthe container I2 and the scraper 3I and propeller 33 are insertedtherein. The cover 2l is then placed on the container I2 and the upperand lower sections of the shafts 32 and 34 are connected together. Whenthe test is ready to be started, the motor 55 is started and through theworm 53 and worm gear 52, the motor vrotates the shaft 32, and therebythe scraper 3l at a constant speed. As the outer shaft 32 is rotated,the bracket 5l which supports the plant wheel 63 is carried aroundtherewith. Since the sun wheel '64 is held against rotation by thetorque meter II, the planet wheel 831 and gear wheel 'It are caused torotate about their principal axes. Gear wheel 'I0 thereby drives thegear wheel ll at a constant speed which in turn drives the propeller 33at a constant speed through the shaft 3d.

It will be apparent that the torque reaction' on the sun wheel 64, whichreaction is measured or recorded by the dynamometer II, is directlyproportional to and only to, the reaction against rotation encounteredby the propeller 33. Since the latter is rotated at a constant speed,the viscosity of the contents of the sample cup I2 is measured at aconstant rate of shear throughout a test.

The agitator 3| and propeller 33 together keep the sample in the cup I2uniformly mixed throughout with respect to temperature and consistency.Films or deposits are not allowed to form on the interior of the cup I2,thereby maintaining an efficient heat transfer relationship with thewater bath I3.

Viscosity determinations of extended range and scope may be accuratelyreplicated with the viscosity apparatus of the invention. The testingconditions may be widely varied in accordance i with particularrequirements.

Since a number of modifications may be made in the foregoingconstruction and different embodiments of the invention may be madewithout departing from the scope thereof, it is intended that all mattershown in the accompanying drawing or described hereinbefore shall beinterpreted as illustrative, and not in a limiting sense.

What is claimed as new is:

l. A unit for use in viscosity measuring appa ratus, which unitcomprises, in combination, a

rotatable scraper adapted to scrape the interior surface of a containeradapted to hold material for measurement of its viscosity, a first shaftsecured to said scraper and rotatable coaxially therewith, a rotorrotatable within said scraper, a second shaft secured to said rotor androtatable coaxially therewith, rotatable torque transmitting means onsaid first shaft whereby it may be connected in driving relationshipwith a constant speed motor, a sun and planet differential, bearingmeans supporting the planet element of said differential on the side ofsaid first shaft whereby said planet element is carried around with saidfirst shaft and with respect thereto is free to rotate about its ownprincipal axis., and driving means interconnecting said planet elementin driving relationship with said second shaft. the sun element of saiddifferential being adapted to be held against rotation by a torque meterwith the torque required to so hold said 7 sun element being directlyproportional to the frictional resistance against rotation encounteredby said rotor.

2. A unit for use in viscosity measuring apparatus, said unitcomprising, in combination, a rotatable scraper adapted to scrape theinterior surface of a container adapted to hold material for measurementof its viscosity, an agitator rotatable within said scraper, an outertubular shaft having another shaft disposed therewithin for co-axialrotation therewith, means securing said scraper to one of said shaftsfor rotation therewith, means securing said agitator to the other ofsaid shafts for rotation therewith. rotatable torque transmitting meanson said scrapercarrying shaft whereby this shaft may be connected indriving relationship with a constant speed motor, a sun and planetdifferential, bearing means supporting the planet element of saiddifferential on the side of said scraper-carrying shaft whereby saidplanet is carried around therewith and with respect thereto is free torotate about its own principal axis, and driving means interconnectingsaid planet element in driving relationship with said agitator-carryingshaft, the sun element of said differential being adapted to be heldagainst rotation by a torque meter with the torque required to so holdsaid sun element being directly proportional to the frictionalresistance against rotation encountered by said agitator. Y

3. A unit for use in viscosity measuring apparatus including a samplecup and a dynamometer, said unit comprising, in combination, a rotatablescraper adapted to scrape the sides and bottom of said sample cup, apropeller rotatable within said scraper, a hollow shaft secured to saidscraper and rotatable coaxially therewith, a shaft rotatable within saidhollow shaft and secured to said propeller and rotatable coaxiallytherewith, rotatable torque transmitting means mounted on said hollowshaft whereby it may be connected in driving relationship with aconstant speed motor, a sun and planet differential, bearing meanssupporting the planet element of said dlf ferential on the side of saidhollow shaft whereby said planet element is carried around with Vsaidhollow shaft and with respect thereto is free to rotate about its ownprincipal axis, and gear means interconnecting said planet element indriving relationship with said inner shaft, the sun element of saiddifferential being adapted to be connected with said dynamometer andheld against rotation thereby with the torque required to so hold saidsun element from turning being directly proportional to the frctionalresistance against rotation encountered by said rotor.

4. The unit called for in claim 3 wherein each of said shafts isprovided in sections adapted to be coupled together and uncoupled asdesired.

5. Viscosity measuring apparatus, comprising, in combination, athermostatically controlled water bath, a sample cup supported in saidbath, a condenser cover on said cup, a rotatable scraper adapted toscrape the side wall and bottom oi' said cup, a propeller rotatablewithin said scraper, a hollow shaft secured to said scraper androtatable coaxially therewith, a shaft rotatable within said hollowshaft and secured to said propeller and rotatable coaxially therewith, asynchronous motor, a vworm and worm gear combination interconnectingsaid hollow shaft in driving relationship with said synchronous motor, asun and planet differential, bearing means supporting the planet wheelof said differential on the side of said hollow shaft whereby saidplanet wheel is REFERENCES CITED The, following references are of recordin the le of this patent:

UNITED STATES PATENTS Number Name Date 1,334,856 Hayes et al. Mar. 23,1920 1,836,995 Stickney Dec. 15, 1931

